Laminated windows are made up of multiple plies, e.g. two plies, made of glass, plastic, or glass/plastic substrates that sandwich one or more interlayers. The windows are widely used in automotive front windshields and sidelights. Typically, laminated windows must exhibit one or more of the following properties: (1) high impact energy absorption; (2) shear and tear strength sufficient to prevent rupture of the interlayer by broken glass; (3) sufficient adhesion between the interlayer and the glass to prevent dispersion of broken glass; and (4) good optical qualities.
Depending on the vehicle and the application, a laminated window may need to exhibit additional properties such as, but not limited to, (a) resistance to ballistics, blast, and wind pressures, (b) sound reduction and/or (c) solar control properties. One of the conventional ways for changing the properties of a laminated window is to modify the composition and/or configuration of the interlayer(s).
Conventionally, laminated windows have a polyvinylbutyral (PVB) interlayer that includes various plasticizers. Different plasticizers are added to the PVB to change the properties of the interlayer.
One of the drawbacks of a laminated window having a PVB interlayer is cost. In order to be formed into a sheet that can be used as an interlayer in a laminated window, PVB must first be extruded. Extrusion is the process of converting plastic pellets into cut-to-size sheets of plastic using specialized equipment that subjects the pellets to both heat and pressure. Extrusion can be an expensive process.
It would be desirable to have a laminated window that includes an interlayer that can be formed via a non-extrusion process, such as a cast-in-place process or a reaction injection molding (RIM) process. The present invention provides such an interlayer. The interlayer of the present invention comprises a polyurethane material that can be incorporated into a laminated window. The laminated window of the present invention exhibits good sound attenuation properties.